SAML 2 AuthnContext Schema Problems

<xs:complexType name="PasswordType">
    <xs:sequence>
      <xs:element ref="Length" minOccurs="0"/>
      <xs:element ref="Alphabet" minOccurs="0"/>
      <xs:element ref="Generation" minOccurs="0"/>
      <xs:element ref="Extension" minOccurs="0"
        maxOccurs="unbounded"/>
    </xs:sequence>
    <xs:attribute name="ExternalVerification" type="xs:anyURI" use="optional"/>
  </xs:complexType>

  <xs:element name="RestrictedPassword" type="RestrictedPasswordType"/>

  <xs:complexType name="RestrictedPasswordType">
    <xs:complexContent>
      <xs:restriction base="PasswordType">
        <xs:sequence>
          <xs:element ref="RestrictedLength" minOccurs="1"/>
          <xs:element ref="Generation" minOccurs="0"/>
          <xs:element ref="Extension" minOccurs="0" maxOccurs="unbounded"/>
        </xs:sequence>
        <xs:attribute name="ExternalVerification" type="xs:anyURI" use="optional"/>
      </xs:restriction>
    </xs:complexContent>
  </xs:complexType>